It's a Long Story
by Starlight05
Summary: Sherlock was one of the most frustrating people John had ever met. He was stubborn and arrogant and far too intelligent for his own good. More often than not he seemed to go out of his way to try to John completely, irrevocably insane. But all of that didn't mean John wanted Sherlock to die. AU in which John is a mere mortal, and Sherlock is ... something more.
1. Part One

**LOL I meant to post this like two weeks ago when I put it on AO3 but forgot... well, better late than never.  
**

 **This is heavily, heavily inspired by the premise and events of the tv show Forever (which was cancelled before its time to be frank), but you don't need to have seen the show to read this fic. If you have seen the show, you'll know what I mean when I say that Sherlock is Henry Morgan (not literally, but he's got the same thing going on). No copyright infringement intended. I don't profit from this anyway, so it shouldn't matter that I'm borrowing from Forever's brilliance (and Sherlock's too, duh). Anyway, you all should watch it; there's only one season but it's lovely. But read this first ;)**

* * *

Sherlock Holmes was one of the most frustrating people John had ever met. He was stubborn and arrogant and far too intelligent for his own good. More often than not he seemed to go out of his way to try to John completely, irrevocably insane.

But all of that didn't mean John wanted Sherlock to _die_.

A single phone call was all it took. Just one call, barely ten seconds long, was all it took for John's world to shudder to a stop. Or perhaps to screechingly stop, then burst into flames. After that call, he was out the door a few seconds, med kit in hand and Sherlock's shaky words, laced with agony, reverberating in his ears.

 _"Crime bosses... Ambush... Need assistance... Alley in Soho."  
_

It took Sherlock a few minutes to get a text with a more exact location sent, but by then John was in a cab, well on his way in the general direction of his mad flatmate.

The ride over seemed to take several eons, but finally - though it couldn't have been much more than ten minutes - John tumbled out of the cab and dashed down the dark lanes Sherlock had described. He at last spotted Sherlock, though it took a few aching moments of frantic running. The consulting detective was sprawled by a row of rubbish bins, half-hidden in the shadows between buildings.

"Sherlock," John called, breathless in spite of his medical training, panicking in spite of all his time as an army doctor. "It's okay, Sherlock, I'm here." He staggered down the alley and collapsed onto his knees next to his flatmate, who was gasping for breath and coughing feebly. John's eyes flew over Sherlock, assessing. What he saw was far from promising: a dark stain was spreading steadily across Sherlock's clothes, the blood shining on the man's slender fingers where it spilled over them, heedless of his feeble attempts to stem the stream. Scrambling, but taking deep breaths to steady himself, John yanked his phone from his pocket and dialed 999.

"Hello, yes, I need an ambulance," he replied to the operator, trying to keep his focus as he detailed their location. "I have a stabbing victim. Looks like one wound to the abdomen. Can't tell if the lung has been punctured, but breathing has definitely been affected."

The operator asked a few more questions, and John answered as calmly as he could, but his concentration was threatened by Sherlock's hand gently grasping at his sleeve, as if he were drowning and John were his only lifeline.

John hung up the phone and dropped it, moving closer to Sherlock and feeling a jolt of horror as he pulled back Sherlock's coat and examined the wound more closely.

"I believe it's too late, John," Sherlock choked out. There was a thin trickle of fluid at the corner of his mouth, and John yanked on his gloves stored in the med kit, forcing them over his shaking fingers. Any instinctive focus, reinforced from his time in Afghanistan, felt remote and unreachable as fear made John's heart hammer and his head spin.

"Hey hey hey, don't think like that," John said quietly. "It's not too late." He brushed away the blood from Sherlock's lips with a small square of gauze, then pressed his hands over Sherlock's, the scarlet creating a terrible contrast to the brilliant white of the gloves. Sherlock grunted softly, face contorting with pain at the heightened pressure.

"I'm sorry," John whispered. He slid one hand off Sherlock's chest and into the first aid kit, rummaging for something, anything else to help. "An ambulance is on the way. You'll get help, they'll fix you up, I promise."

But Sherlock just shook his head. "I doubt that. I took too long getting to the phone to call you." He reached up with a shaking hand and grabbed John's other wrist, trying futilely to tug it away. "John, just stop."

"What?" John was sure he was looking at Sherlock like he was mad. "No, Sherlock, you need me right now. I'm not going to let you-"

"John." It looked as if Sherlock were smiling, but that couldn't be. "Come on, just let go."

"No, no," John shook his head. "Don't be ridiculous. You-you're going to be fine."

"John." Sherlock, despite his state, still managed to summon enough snark to roll his eyes. "You're an army doctor. Surely you've seen wounds like this before. You know I am far from fine."

"Dammit, where is that ambulance?" John murmured, looking toward the street. It had barely been four minutes since he had made the call, but surely by now...

"John," Sherlock's voice turned urgent suddenly. Not to mention weaker. "Please, listen to me. I shouldn't have called. I'm sorry. Let me go."

Without warning or bidding, John's eyes filled with tears. "I can't do that, Sherlock."

"You have..." Sherlock coughed again but forced himself to continue through what was obviously a fresh wave of intense pain. "You have... no choice. I'm sorry, John."

His eyes closed then, and John felt him take a shuddering breath, lungs sounding weaker by the second. "Run."

John blinked, confused. "No, no, you're... You're not making any sense. Sherlock, I'm _not leaving you_."

"...Please. Get out of here..."

He exhaled once more, and John waited, heart in his throat, for him to inhale again. "Sherlock," he stammered, hands tightening on the wound without volition. "Come on, please, don't do this. Don't you give up, you bastard. Answer me!"

But the detective didn't respond, or inhale. There was nothing, no movement in the body beneath John's hands. "Sherlock!" he cried, just as lights and sirens came blazing - at last - into view. His fingers fumbled at Sherlock's neck, groping for a pulse. "No, no, no..."

Nothing.

"No," he whispered, a tear sliding down his cheek. "Come on, Sherlock-"

But then, the impossible happened. Quite literally. One moment, John was holding his dead flatmate in his arms, and the next, he was clutching at nothing but air and shadows. Somehow, Sherlock was gone.

"Sherlock?" John cried, as if calling out would bring him back. He turned, scouring the dimly lit alley frantically, almost expecting Sherlock to leap out from behind a bin and laugh at the brilliant prank. But all he saw were the paramedics removing a stretcher from the vehicle. John whirled around in panic. Sherlock wasn't there. But he couldn't be _gone_. It was impossible.

What was John supposed to do now?

 _"Run... Get out of here."_ Sherlock's final words. Without considering other options, simply reacting as he always did in compliance with his friend's inexplicable commands, John turned away from the paramedics and dashed down the alley.

* * *

He wandered through London for what felt like hours, becoming increasingly lost. He'd never been in Soho on foot much, and his desperate flight from the alley had left his internal compass spinning. Not to mention being out this late into the night also meant virtually no foot traffic, and it seemed the cabs were anywhere but here. Somehow he couldn't even find a Tube station.

Eventually, when John's feet were aching and his hands shaking from the cold wind, he sat down on the steps of some unknown doorway and buried his face in his hands. He took a deep but unsteady breath and tried to convince himself it didn't sound like a sob. There were damp streaks on his face, and he brushed them away quickly.

"Sherlock," he whispered. "Where are you?"

Even as he said it he knew he answer. Sherlock was dead. He had seen it himself, felt the blood, the lack of pulse or breath. The fantastical and inconceivable _thing_ that had happened after was just a result of shock; it was his imagination and nothing more. It had to be.

But the realization that John must had abandoned his best friend's body in an alley made him want to cry all over again. That wasn't what Sherlock deserved.

"Oh Sherlock, I'm so sorry."

"It's alright, John."

He whipped his head up so quickly he was surprised he didn't break any vertebrae. But that thought was chased away by what he saw before him. Sherlock stood there, looking just as he had earlier that day: clean, white shirt, dark suit jacket and trousers, his coat collar turned up and his curls in their usual artful disarray. He looked at John with an apologetic look in his eyes, an expression John might even call gentle.

This must be what going mad feels like, John thought.

A few seconds passed before John could remember how to vocalize words. "Sherlock?" His voice came out broken and small.

In response, the detective took a small step forward. "Yes," he replied after a pause, and nearly smiled. "Sorry about... earlier."

John reached up and grasped Sherlock's forearms, both out of a desire to touch the living warmth of the man he had been sure was dead and out of a need to steady himself. "I don't understand." His words came out hoarse and uncertain, but a bit stronger this time. He realized that at some point, he must have stood up, because his height on the step now equaled Sherlock's on the pavement below.

The expression that flashed briefly in Sherlock's eyes was one of concern and perhaps even sympathy. "John, I... I owe you a thousand apologies. This was not at all the way I intended to tell you, and-"

But John's grip tightened, and he gave Sherlock a rather violent shake as all the fear and anger boiled up to the surface without warning, pushing back the shock and confusion. " _Apologies_? You think you can just _apologize_ for that and everything will be fine again? I watched you _die_ , Sherlock Holmes! You bled out in my arms because I wasn't quick enough to find you! You died and I couldn't stop it and then I had to run away from you because you went and _died_ on me, you bastard! An apology isn't going to fix this! I... I thought... I thought you were dead... I thought... you were dead."

He may have started out yelling and shaking his flatmate, but by the end, his voice had somehow dissolved into a whisper and his forehead was pressed against Sherlock's chest, his hands still gripping Sherlock's arms. Suddenly, unexpectedly, relief washed over him as he felt Sherlock's pulse, strong and steady, thumping away in his ribcage beneath John's forehead. That sensation, more than any of Sherlock's words or gestures, washed some of John's anger and fear away.

A few moments of the two of them being locked in this odd embrace passed, and then with an uncharacteristically careful touch, Sherlock pulled away, though he left his hands on John's shoulders where he had placed them. "I'm not dead," he murmured, though such a statement was rather unnecessary now. "It's alright."

John swallowed. "Sherlock... What is going on?" he asked in a weak voice.

"It's a long story," Sherlock murmured, eyes dropping to the pavement. A slight smirk seemed to be fighting for dominance on his face, though it didn't quite reach his eyes.

"I don't care," John retorted. "I just watched you die. I need to know how the bloody hell you're standing here."

Sherlock looked back up at him, eyes intense, as if he were taking the full measure of John. Finally he nodded. "Come on then," he replied as he stepped away toward the street. "I'll explain everything. But first, let's go home."

* * *

By the time they returned to Baker Street, John felt that his shock had - mostly - worn off to a dull buzz, like he had taken a shot of adrenaline directly to the heart and was still coming down from it. Sherlock paced back and forth in the sitting room, running his fingers through his curls. Finally, John had had enough, and grasped his wrist. Instinctively, his fingers sought the taller man's pulse, and felt it thudding away, strong and steady as if nothing had happened earlier.

"Am I going mad?" John asked. "Did you give me some sort of hallucinogenic drug again?"

Sherlock smiled faintly, though something seemed off in his countenance. "No, not this time."

"Then what did I see? You couldn't have died."

Sherlock shifted but made no move to pull away, just shuffled his feet and avoided John's gaze. It occurred to him then that Sherlock seemed nervous. "What's wrong?"

"It's just... it's been years since this situation has happened, and the last time it did, the reaction was not exactly relief."

"What are you talking about? You were mortally wounded... or something! Since when would anyone express relief at that?"

"No, John," Sherlock whipped his gaze up, suddenly imploring. "I mean relief that I returned."

"Re..." John breathed, as the full implication of that sunk in. "You mean you really did die? And you... came back?"

Sherlock just looked at him, oceanic eyes soft and worried. He didn't move in protest as John stepped away, letting go of his wrist. "You died and came back," John reiterated. "I don't understand. I have to be going mad. This is ridiculous. It's impossible. It's... it can't be."

"It can," Sherlock said. "And yes, it is actually both ridiculous and possible. I could... prove it to you, if you'd like."

Before John could move to stop him, he stepped into the kitchen and picked up a small paring knife, which he lifted to his left wrist. Biting his lip, he glanced up at John.

But John was already in motion, jerking Sherlock's hand away and seizing the knife, tossing it toward the sofa, where it lodged itself deep in the cushion. "What the hell do you think you're doing?!" he yelled, shaking Sherlock. "I only just got you back! Maybe you're the one who's gone mad!"

Sherlock hushed him, leaning into his grip. "No, no, John, listen. I _can_ prove it to you." He huffed, looking flustered. "It's just been some time since I had to do this _after_ the fact. I'm a bit out of practice, assuming I was ever accustomed to this."

"You cannot ever do something like that again, do you hear me?" John snapped, hardly listening to Sherlock's resigned words. "I knew you were foolhardy, but..." He shook his head.

Sherlock watched him, clutching at his arms, as they had been doing for what felt like all night to John. "You still want proof?"

"Not that way," John whispered, eyes flashing to the knife then back. "What would you be proving, anyway?"

His flatmate straightened then, taking a breath. He met John's gaze resolutely, and then, with an oddly formal tone, proceeded to tear down John's conception of how the universe worked.

"I was born in 1782. I have died or been killed several dozen times since. As you can see," he nodded down at himself. "None of those deaths took any permanent hold."

John felt frozen. He stared at Sherlock, looking him up and down, his own body tense. He half-expected at any moment for Sherlock to give an abrupt grin and shout "April Fool's!" but the moment never arrived. Instead, evidence poured into his conscious mind as if of its own volition.

Sherlock's oddly elevated way of speaking. His disdain and misunderstandings of social media and modern slang. His frighteningly extensive and detailed knowledge of crimes and criminology, which spanned decades at least, if not centuries. His struggle to discern and exhibit accepted social norms and behaviors. Current ones, at least.

The way his pulse had stopped, the way he had literally vanished then reappeared looking not at all worse for wear.

John felt the ground sway beneath him and Sherlock's hands tighten around him. Then, darkness.

* * *

"John?"

He blinked, realizing in that moment that at some point, his eyes must have closed. Sherlock's face swirled into focus, forehead creased with worry as he gazed down at John, who was now slumped on the sofa.

"Did I pass out?" he asked, taking the glass of water Sherlock was proffering.

"Nearly. I'm sorry. It occurred to me that the last time I did this, the person in question had already been sitting." Sherlock shook his head, self-deprecating tone matching his exasperated expression. "I'm sorry for the chaotic way I'm going about this."

"Alright, you can stop apologizing now, it's getting a bit unnerving." John sat down the glass and shifted. Sherlock had evidently helped him to the sofa, though the detective himself was sat on the edge of the coffee table facing him.

"You did take it better than others have in the past."

John met his gaze. "How far in the past? Since apparently you're _immortal_? Could you elaborate on that, maybe, by the way?"

Sherlock smiled, though the warmth seemed superficial. "Shall I start at the beginning?"

John nodded, fingers finding Sherlock's wrist again, evidently of their own volition. "Please."

Sherlock shifted on the table, holding John's gaze. "In the summer of 1815," he began, eyes glazing over somewhat as he mentally traveled back. "An accident occurred which resulted in my death, which would prove to be the first of many deaths, though I was not to know it at the time."

"What sort of accident?"

"I had been working in Switzerland for a brief span, a favor to a family member, when I learned of a criminal plot that was being put into motion by another man staying in the same inn. Naturally, I stepped in to prevent it, but my interference resulted in a confrontation with this man by the side of a waterfall, and..." Sherlock scowled. "You can surmise what came next, I assume."

"You fell." John shuddered at the thought.

"The man, Moriarty was his name, managed to gain the upper hand, the footing was slick and precarious, and I took my eyes off him for a moment as I attempted to regain my balance. He seized that window of opportunity to push me backwards. And while I did pull him down with me, thus foiling the plot he'd masterminded, I still... died."

John stared at him, incredulity and denial clamoring for attention in his mind. "Sherlock," he murmured. "You realize what you're telling me doesn't make any sense. It isn't scientifically possible."

"You saw," Sherlock said, earnest and imploring. "Tonight, you felt my pulse stop, did you not? You saw me stop breathing, you saw me die, and then you saw me disappear."

"Yes, but-"

"I am well aware that there is no scientific precedent for this, but I cannot deny the evidence of my own body and mind. Something happened to me that night in Switzerland, which I believe resulted in my... condition. Unfortunately, I have never discovered the reason." Sherlock dropped his gaze. "It's not a curse I disclose to many, John, for it does have its... quirks."

"What, you mean besides the whole coming-back-to-life bit? What other 'quirks' are there?" John chuckled, though it came out half-hysterical.

Sherlock let out a bitter laugh. "When I return, I always awaken in the nearest body of water, my body renewed to its previous state, a healthy 33-year-old. And... I never have clothes when that occurs."

John blinked, the image of a very naked Sherlock (nothing he hadn't seen before, honestly) climbing out of the Thames River and attempting to navigate the streets of London without a stitch on his pale body. "Um..."

"Another way the homeless network comes in handy." Sherlock chuckled dryly. "They arrange for changes of clothing to be stored in various drop-points along the Thames. It's a luxury compared to having to simply muddle my way through, pretending I had been robbed and the like."

"I don't understand. Why... Why is any of this happening?"

Sherlock shook his head. "That is an ongoing investigation, John." He seemed to be putting conscious effort into avoiding John's eyes.

"So... your family...? From the 1700s?"

"Dead, of course. And after my journey to Switzerland, I did not return to London until well into the late 1800s. Nor can I stay in one place for too long, lest I subject myself to suspicion or persecution. And with the advancements in technology in the past decades, especially in terms of surveillance and government record-keeping, remaining inconspicuous with a believable cover identity has become increasingly problematic."

Sherlock's expression showed a flash of something then, something John would have missed entirely had he not been watching the other man with such intent. The look portrayed, for a mere instant, what seemed to be decades, or rather centuries, of loneliness and weariness. What must it be like, John wondered, to watch everyone around you live, age, and die, yet you remain the same? How can anyone make friends, knowing they will just lose them?

Then he realized what thinking in that way really meant. "Oh, bloody hell," he groaned, leaning back on the sofa.

"What?" Sherlock asked, voice laced with worry. Expecting rejection, contempt, who knew what else.

"I believe you. Bloody hell. Why do you always have to be so articulate and persuasive?" John rubbed his eyes, chuckling. "Or maybe I've just gone as insane as you."

When he looked back up, Sherlock was smiling too, just slightly, a gesture that was still overbalanced by the quiet melancholy light in his eyes. "Well, having an ally who is not Mycroft _is_ a change for the better."

"Yeah, what about Mycroft? He's obviously not really your brother..."

Sherlock huffed. "He appears to be a great-great-great grandchild of a second cousin of mine, from what he and I have established about our family tree. Of course, no one would believe us if we were to tell people that, so to the rest of the world we are siblings."

"So he got you your current identification, I take it."

Sherlock nodded. "This entire arrangement was made easier by the fact that Mycroft is an only child and his parents passed away ten years ago, well before I returned to London. I had heard news while in France - my home prior to this flat - of a Mycroft Holmes who was rising in the British government's ranks, and I could not resist investigating further, especially with a first name like that. Our family has always been one with a penchant for unusual names. His reaction to finding out about my curse was, thankfully, more fascination than condemnation."

But John's ears had perked up. "So Sherlock Holmes really is your name?"

Sherlock nodded. "I have only used it in my first years of life before my initial encounter with death. I use aliases otherwise. After all, the name Sherlock is not exactly common, after all, which makes me even more distinctive a figure. Having Mycroft as family made returning to my true name feasible."

He stood, that tight, fake smile still on his lips. "Here, I have something to show you." John watched as he strode into his bedroom, from which shifting and rustling noises soon emanated. Sherlock returned with a large photo album, which he promptly laid across John's lap.

The binding appeared fairly new, but upon opening it to the first page, John realized that contents were anything but recent. Inside was an ancient newspaper clipping, detailing the incident of Sherlock's original death in Switzerland. The paper was yellowed and faded almost past the point of readability, but John could make out a word here and there, enough to glean the general message.

As he flipped through the next few pages, he saw that the book contained small bits of evidence, artifacts from certain times in Sherlock's life, or more accurately lives. There was the record of a ship journey to North America, a university diploma from a US university, then more compelling evidence: photographs. Sherlock appeared in a plethora of locations, over a massive span of dates, but in each he was unchanged. Certainly, he had varying hair and clothing styles, but his face was the same.

John looked back up at his flatmate, who was still peering over John's shoulder at the photograph of himself in the New Zealand countryside from what was labeled as the 1910s, an almost wistful glint in his eyes.

"I can't imagine what this must be like," John breathed, suddenly so very sorry. He rested his hand on Sherlock's arm.

Sherlock nodded slowly. "Thank you for not throwing me in a sanatorium."

John burst out laughing, though that was likely partially motivated by shock and not any humor in the feeble joke. He rubbed Sherlock's shoulder. "You'd burn down the place out of sheer boredom. There's no way I would subject the other patients to a tantrum like that."

Sherlock smiled, this time with genuine emotion, biting his lip and ducking his head. Self-conscious, but it was still a real smile. John felt warmth spread through his whole body at the sight. This night had been the most difficult of his life, no competition, but the fact that he knew this was trying for Sherlock too made it better. The man had just been murdered, then had to expose his greatest secret to his flatmate, whom he'd only known for a tiny fraction of his inconceivably long life.

So that smile seemed rather like a step in the right direction.

* * *

The path down the right direction proved a bumpy one, John discovered over the next few months. After the night of Sherlock's death, return, and subsequent revelation, the two flatmates attempted to return to some semblance of how their lives had been before. However, John found himself noticing the inevitable alterations.

The smaller things were simpler: John often stared avidly at Sherlock after spending time with his artifact album, trying to imagine what he may have been like a century ago, how he may have spoken or behaved. Had Sherlock always been like this, stubborn and curious and taciturn and passionate? And what evolution would a person's character undertake in two centuries, considering how intensely people could change during a normal life span? He tended to think it would be a vast change, but he declined from asking; that query just seemed too personal.

Sherlock did, however, invite John to ask him about the album, which John did eagerly. This led to many nights (ones without cases, of course) whiled away by the telling of stories of Sherlock's mad life. He had lived in over a dozen countries, visited over one hundred, and was fluent or conversational in ten languages. He returned to university periodically to acquaint himself with the thinking of the day, receiving a different degree each time but taking care to read some general classes as well. The adventures he had had were as wild and varied as his own knowledge, ranging from amusing to fascinating to exciting to saddening. John had a feeling that Sherlock had many other tales than the ones he shared with John, ones he did not share with anyone. John suspected, judging from some of the photos in the album - ones depicting Sherlock with people who might have been his friends - that they were tales of loss. It was no wonder, he mused often to himself, that Sherlock behaved so anti-socially sometimes; he appeared to fluctuate between social periods and stages of shielding himself from further grief as best he could.

This seemed to be the largest group of friends that Sherlock had had in ages - Mycroft, Lestrade, Mrs. Hudson, Molly, and John himself - and though Sherlock would insist on referring to them all as acquaintances, John knew better.

Only a handful of days after Sherlock's revelation of his true nature, Mycroft made an appearance at their flat, where he and John spoke for nearly an hour about the logistics of Sherlock's "situation," as well as to inform them both that the criminals responsible for Sherlock's most recent death had been sighted fleeing the city and incarcerated. John brushed off that information - good riddance to them, anyway - in favor of grilling him. According to Mycroft, there was a system in place in case of a sudden death on Sherlock's part, one which would enable Mycroft's men - well paid for their silence and discretion - to get to him as quickly as possible. Apparently, Sherlock had suffered more than one bout of hypothermia thanks to his reentry zone in the past, and Mycroft, fiercely dedicated to the safety of his "brother," was determined not to allow that to happen on his watch. When he left, John himself felt more protective of Sherlock than ever. Perhaps Mycroft's guardian sensibilities had set him off, but for weeks following that visit, John found himself looking for ways to defend Sherlock in any way he could, whether during cases or at Scotland Yard in the face of the officers' ridicule or from his bouts of debilitating boredom. The man had been through enough throughout his life without suffering more needless pain, even minor amounts of it.

But it wasn't as if Sherlock could really die, after all, he continually reminded himself. Regardless of what he told his own mind, four months later, John was still waiting for that protective instinct to fade.

* * *

Sherlock may not have been able to die, but that did not prevent him from still being composed of flesh and blood. This was a fact John was, at the moment, intensely aware of, as he watched Sherlock flinch and bite his lip in an attempt to not make noise. John heard a soft, sickening sound he didn't want to dwell on, and then Sherlock's hand was free of the handcuffs at last.

"Hold on," he breathed urgently, eyes shining with pain as he cradled his newly-wounded thumb to his chest. Within instants he had opened the cuff enclosing his other wrist and dashed to John's side. "Mycroft will be on his way by now."

"Will you at least admit _now_ that we were right to warn him of our plan beforehand?"

Sherlock scowled at him even as he pressed his good hand to the bleeding wound in John's right leg. John cursed under his breath at the sudden pressure. "Well, I won't say I told you so."

"Shh," Sherlock froze then, head rising. "He's coming back."

Both tensed as Evans' footsteps approached. The criminal, a gun smuggler for a gangster operating in New York, had come to London to flee the United States task force but had instead inevitably found himself in Sherlock's grasp after shooting one of the consulting detective's best homeless informants in the knee. Unfortunately for Sherlock and John, Evans had not gone down without a fight, and had held the two men captive for the past three hours.

The gunshot wound was new, though, and it told them that Evans was getting desperate and scared. Not a good combination.

"Sherlock," John hissed. "Artery?"

Sherlock's eyes were too afraid for it to be anything else, and that combined with John's weakening body told him his suspicion was correct.

"Hold on, John."

As John lost consciousness, the last thing he heard was loud bangs and the sound of Sherlock yelling.

* * *

John came back to consciousness, somewhat, after what felt like an age. It felt as though he were moving in slow motion while the rest of the world rushed on ahead. Mustering all the concentration he could, he made out the sound of voices, one flustered but professional, the other familiar and peeved. The latter was speaking, voice strained.

"What do you mean, out of B negative and O negative? What sort of operation is this? He doesn't have enough time to wait for another shipment of either, look at him! He's lost at least a liter of blood, probably more. You _cannot_ be _out_!"

"Sir, we need you to calm down. We've closed the wound, so he won't be losing any more blood. All we have to do is-"

"Take mine."

"I beg your pardon?"

"Your supplies of blood are pitifully low or of the wrong sorts, time is of the essence, and my blood type is compatible with his. Therefore, take mine."

"You're offering to give him a transfusion?"

"Is he at risk of contracting hypovolemic shock?"

"... Yes, he-"

"Then take my blood. However much he needs."

There was a reply to that, but John was struggling to follow the conversation at all, let alone make out the soft response. He did manage to force his eyes open.

"Sh'lock?" Moments later he felt Sherlock's hand on his, and his flatmate's face swayed into view.

"John. Hold on, it's alright."

"Sher... Where am I?"

"You're alright, you're in hospital. We'll fix you up now, alright?"

John tried to move his lips to answer, to make his vocal cords work with his brain, but he felt himself fading from consciousness again. "Sh'lock."

"John, no. Don't leave me yet, alright? Stay awake."

"Sher..." But his eyes flickered closed before he could finish the name.

* * *

Hours later, or so it seemed from the darkness beyond the window panes, John regained consciousness. He lay there in the hospital room, the lights off, and wondered what had happened. The last thing he remembered clearly was mouthing off a bit too much to Evans, who had not taken it kindly. After that... mostly he remembered the pain, the numbness, the worry when he realized there was more blood than there probably should have been. And Sherlock, he remembered Sherlock.

Where _was_ Sherlock? Had he been shot too? No, John recalled his voice earlier, something about staying awake. If Sherlock had been speaking, he could not have been dead. Then again, death and Sherlock had an unconventional relationship...

His faintly muddled train of thought was derailed when a rustling beside him made him start. "John?"

"Sherlock," John sighed in relief. "Still alive, I see."

"Very funny," Sherlock muttered. John heard more movement, and then a lamp clicked on, flooding the room in a soft, white-yellow glow.

Sherlock looked tired, but relieved. His skin seemed even paler than usual. There was a small cut on his cheek, a splint on his thumb - which had been broken during his efforts to escape the handcuffs and help John, he now recalled - and an IV in his arm, its contents scarlet.

"Sherlock," John frowned. "What happened?" He moved to gesture at the line, when a thin cord on his own arm gave him pause. His eyes trailed along its length to see where the two ends met at the bag, filled with more scarlet fluid.

"You don't remember? I thought not; you seemed quite incoherent when you woke last."

"I woke up?"

Sherlock chuckled. "Briefly."

"What happened, Sherlock?"

"After you lost consciousness, I managed to disable Evans. He really was unstable, hardly thinking straight, so it was not difficult. Some of Mycroft's goons arrived shortly after, and we were transported to the hospital." He gestured to John's leg. "The gunshot wound only nicked rather than severed your artery, it seems, so they were able to repair the damage with a minimal amount of difficulty. You did require a blood transfusion, however, but according to the doctors here, you will not sustain any lasting damage from this situation."

"You're giving me blood?"

He huffed, looking self-conscious. "This place was disappointingly low on the necessary types of blood. Some sort of clerical snafu, apparently, so I offered. You had lost too much, John, I had to do something." He looked away, shrugging nonchalantly, trying to save face it seemed.

John smiled at him. "Thank you."

Sherlock shook his head. "It was nothing."

"But you're alright?"

"Yes, fine, other than this," he lifted his injured hand. "And my disappointment. That case was barely a five in the end. And it had held such promise..."

"There will be other cases."

Sherlock nodded, lifting his gaze to meet John's. He leaned forward in his seat, clearing his throat. "It is not in my nature to say this, but... thank you, John."

Bemused, John gave him an uncertain smile. "For what, Sherlock?"

"Not leaving yet." Sherlock smiled back.


	2. Part Two

Just over six months later, nearly a year after Sherlock's world-shaking reveal, John found himself dashing down an alleyway after his mad, immortal, stubborn flatmate. Six months of having a relatively calm life - for them - with not a single near-death experience for either man. Life was good, and John found - amazingly - that he was actually mostly used to the idea of having an immortal flatmate. Both men had acclimated to their new dynamic, and in fact were flourishing.

So when a new case had come in from Mycroft, an intriguing series of near-flawlessly executed kidnappings and extortion schemes, they had accepted. Sherlock had hardly even complained, too pleased at the level _eight_ case before him to fuss much about its source.

Five days later, days which had been full of interviews and CCTV-reviewing and dead-end chases down the paths certain leads had left behind, John and Sherlock were close, _so_ close to ending it. Sherlock had identified the perpetrators, a particularly ruthless band of men bent on revenge after having their pleas for "justice" ignored by the British government. It seemed they had campaigned for certain laws to be adjusted to benefit their company's profit margin. However, Sherlock had discovered that the company had been gaining their income through underhanded methods, including blackmail and outright threats. The appeals to the government had been nothing but smokescreen at first, though now that their enterprise was collapsing - thanks to the economy and an apparent shuffle in leadership recently - they were floundering and growing desperate. Thus their kidnapping of some of the lower government officials to demand money.

The evidence was amassed, the case against them firm. All that remained for Sherlock and John to do was to find them.

The afternoon of the fifth day arrived, and Sherlock's keen nose had sniffed them out: they were holed up in one of two old, currently shuttered business centers of theirs (buried cleverly in the records until Sherlock had got to them) in Brighton, waiting for a getaway driver of theirs to arrive so they could escape the country. Sherlock had confided in both John and Mycroft that he believed the group was planning to smuggle themselves out of the country to escape prosecution. What they did not know, though, was that Mycroft's men had already intercepted the driver, so the men were now waiting ducks. Unfortunately, they were also highly dangerous, Sherlock assured, and were likely well aware they were being tracked. But as long as he and John remained inconspicuous, and Mycroft's men were out of sight when they made their move, they would be fine.

That evening, they arrived in Brighton, and split up: Mycroft's team moving in one direction, Sherlock and John in another. There were two locations in Brighton where Sherlock said they were most likely to be hiding, so they would separate until confirmation could be made.

However, the plan almost immediately disintegrated. Moments after Sherlock and John stepped out of their car, blocks away from the first site just to be safe, shots rang out. Both ducked, then ran into the winding streets.

"I think we're in the right place!" John called, trailing steps behind Sherlock and his billowing coat.

"Call Mycroft!"

"I'm sure he's already mobilizing the others." John risked a glance over his shoulder and spotted a dark-clothed figure sprinting after them. "We've got to lose this bloke and make our way back around to the pier." The pier was their prearranged rendezvous should something go wrong; it was based on a calculated gamble, but Sherlock claimed the men would not harm innocents, only those they believed deserved the rough treatment. So going to the pier, hiding in plain sight among the crowds, was their best bet. Risky, but no one else had had a better idea.

"Follow me!" Sherlock tossed over his shoulder. He turned nearly ninety degrees and ducked down an impossibly narrow lane. John put his head down and followed.

Tiny shops blurred past him as he darted by shoppers and ducked through spaces small enough to be alleys, but which were apparently still considered streets. He dodged around more people, pushing and knocking things over when he had to, doing anything and everything to keep Sherlock in sight and to lose the criminal chasing them.

The whirlwind of enclosed space, noise, and people was disorienting, though, and when John turned what had to have been the tenth corner, he pulled up to a screeching halt. Sherlock was gone.

John spun in a circle, bewildered, heart pounding. What the...? Sherlock had been there, just ahead it had seemed, mere moments ago. How had they got separated? Unless that dark coat he'd been following the past few turns had not in fact been Sherlock's, but who else dressed that dramatically?

Shaking off his confusion, John began moving again. If anything, he could duck into a shop and ask for directions to the pier. It was clearly quite easy to get lost in this area of town, so there was a chance he had managed to lose his tail-

The thought had barely registered in his conscious mind when an arm reached out and dragged him to the side. A sharp pain exploded on the side of his head, and everything disappeared.

* * *

 _I've got to find a safer pastime_ , John thought upon waking, dazed. Rope, or something equally tough, bound his wrists behind his back, forcing his arms to press uncomfortably on the metal chair in which he was seated. He looked up to see two men in dark ski masks surveying him. All three of them appeared to be in an old office, only a few pieces of furniture remaining. The business-center-turned-hideout.

"What do you want to do with him? He's obviously with those coppers. I saw him get out of their car."

So this was the man who'd chased them. John watched warily as he circled him, eyes glinting from within the slit in the mask.

"Wait," the second man said. "I know who this is."

"Who?"

"He's that one bloke, you know, the boyfriend or whatever of that detective from London. Holmes, right?"

Shit. John closed his eyes.

"Sherlock Holmes?" the first man said, sounding alarmed. "So what should we do? We oughta get rid of him now, yeah? Before he can alert the coppers?"

"No," the second man barked as the first moved toward John, hands raised threateningly. "This is why you aren't in charge. We can use him to get hold of Holmes," he added in a whisper that John still heard. He then moved past his companion to grab a fistful of John's hair, which he twisted sharply. "We could probably pinch a few pretty pennies from the Holmeses, couldn't we? So, mate, listen up. Where is Sherlock Holmes? If you're in town, that means he is too. And my friend here chased two of you, so don't bother lying. Where'd he go?"

John met his eyes with as stoic an expression as he could muster in the moment. It helped that he truly did not know where Sherlock had got to, though internally that fact was causing some amount of worry. What if Sherlock was also in danger? Then again, if these two men did not know where he was, there was a chance he was free somewhere.

"Come on, mate," the man snapped, delivering a hard smack to the side of John's head. "I guess we need to use other means of persuasion, won't we?" He signaled to his partner, who grinned and left the room. The remaining criminal straightened, surveying John passively. "Blackmailing the Holmes family..." he mused, an amused tone playing at the edges of his words. "We should have thought of that ages ago. They're loaded."

"Maybe," John muttered. "But they're also not the most generous of sorts."

"Sure," he chuckled. "Though from what I've heard in criminal circles, Holmes the younger will do just about anything for his precious sidekick, won't he? I bet that would extend to giving us a few pounds to ease our way."

There was a scraping-sliding sound from beyond the door, and the man smirked. Whatever the other was bringing, there was no way it bode well. "Once we drain the Holmes' shiny coffers, we'll be off."

"Yeah," the other man chipped in with relish as his back appeared in the doorway. "New Zealand." He was tugging a large tub, the contents of which were sloshing about. It sounded like ice water.

"We agreed South America!"

"When did we say that?"

The second man shook his head and turned back to John. "We'll figure that out later."

No one spoke again as he strode forward, seized him by the scruff of the neck and hauled him upright. John swayed; that blow to the head must have been serious to cause so much dizziness. And so he was unable to resist as he was dragged to kneel before the water, which was indeed filled with ice cubes. He felt the grip on his neck tighten, but could not react as he was shoved forward and down, hitting the water face-first.

* * *

Down into the icy water. Hold. Up. Gasp for air. Repeat.

Nearly all John's perception had narrowed to just that sequence of action. He had no idea how long he'd been enduring this, having lost count around the fifth repetition, by which time he felt his lungs screaming, his vision blurring. Now, his breath - when he was let up - was coming in quick gasps, and his heart felt as if it were pounding quickly enough to burst.

Down again. Hold. Up. Air. And down again...

 _Please, God, let me live_.

Down. Hold. Up. Down. Hold. Up-

"John-!" Sherlock's voice sounded strained and frightened as it burst into John's consciousness without warning, creeping into his notice as if coming from a great distance. But it was enough to send a wave of adrenaline shooting through him. He fought off his attacker's hands enough to lift his head, eyes darting around in search of his flatmate. But his vision was still water-logged and out of focus due to oxygen deprivation, so all he could make out were vague outlines of random shapes in the room.

"Sherlock, get out of-" was all he managed before his assailant wrested control again and shoved him back underwater. His mouth was open at that moment, and he received a mouthful of frigid liquid straight into his windpipe. Coughing, he tried desperately to throw the man off him. But his grip was too strong, and John couldn't see or breathe, and if he wasn't let up soon he would pass out. And if the man kept holding him down while he was unconscious with this water in his lungs...

He could discern sounds around him, muffled by the water and his own clouded brain. But he felt as if he were fading, drifting away. He gasped again, and got another gulp of water into his lungs for his trouble. No, no no no! He couldn't die, not like this, please! Sherlock, where was Sherlock? Sherlock needed him, Sherlock wouldn't let him die, Sherlock would save him so John could keep taking care of him. He couldn't die like this, no no _please_ he had to get to Sherlock, he had to-

The sounds were louder now, and it seemed the man holding him was yelling too. But John could no longer hear them.

* * *

Mycroft, seated in his small office/base of operations near the Royal Pavilion, surveyed the CCTV feeds with an outward facade of extreme stoicism. Inside, however, his mind was racing. He watched as John was pushed under water again, the much larger man easily able to hold him down, especially in his already weakened state. Sherlock, on a different camera, was sprinting down the hallway.

John was jerked up once again, gasping and sputtering. His lips were tinted with blue, even on the video, which did not bode well. If Mycroft's men were even a moment late, John would perish.

"Sir?" the handheld radio on the desk released the garbled voice. "Should we move in?"

Mycroft flinched internally as John was pushed under again, mere instants after Sherlock smashed his way into the room, eyes wide with fear. "Move in now. Remember, shoot to disable if you can. It would be beneficial to keep them alive for questioning. However, your priority is John Watson's safety." He moved to set down the radio again, hesitated, then thought better of ending his instructions there. "And do your best to ensure my brother does not do something insipid."

He leaned forward then, watching the action unfold before him like some sort of sick film. His team moved in, multiple ingress points, and did just what they had been trained to do: disintegrate the violent situation as efficiently and safely as possible. Two wrestled one man to the ground, though more than a few blows were landed in the process. Two others had the unenviable role of dragging Sherlock backwards from where he had been grappling with the other man, whom he appeared to have just knocked unconscious. The final two were dragging John from the tub of water. He collapsed on the soaked floor, immobile. One of the operatives was bent over him, then began attempting rescue breaths. Mycroft's gaze flicked across the screen, fixing on Sherlock's wide eyes as he watched.

Damn.

"Get Sherlock out of the room this instant," he ordered, and was glad to watch his commands obeyed instantly. The man had seen enough death, suffered enough loss, without witnessing John Watson's passing.

"No!" Sherlock had gotten his hands one of the radios. "Mycroft, let me in there! Let me help him!"

The video quality was by no means stellar, but Mycroft could see his shaking shoulders even as he tried to fight off the men. The radio dropped from his hands as he was dragged backwards down the corridor, but Mycroft did not need to hear him to know what he was saying.

"John! No, John! No! John, _please_! JOHN!"

The operative attempting to save John, now pictured on a different screen than Sherlock, abruptly sat back, drawing Mycroft's gaze. "Hayes?" he barked. "What's happened?"

"He's... dead, sir, I'm sorry."

Mycroft dimly registered Sherlock being loaded into a car, still crying out and fighting tooth and nail to return to John, but the other Holmes could only stare at John's body. However, a mere three seconds elapsed between Hayes' pronouncement and the impossible thing which occurred next.

John's body vanished.

* * *

 _Twenty minutes later..._

Mycroft stepped out of the car as it rolled to a stop, feeling shaken and out of sorts. In all his estimations and predictions, he had never conceived of this as a feasible possibility. It was a scenario which had never even occurred to him for more than a few seconds, considered and discarded immediately.

How wrong he had been.

Sherlock's shaking voice was still echoing in his ears as Mycroft strode across the pebble beach near Brighton Pier, though he had left his phone in the car after ending the call with his distraught "brother."

 _"Mycroft. He can't be dead. You should have let me see him. How could you have not let me see him? You should have let me see him..."_

Mycroft had not commented on the choked quality of Sherlock's voice over the line, knowing the man would not have appreciated attention drawn to it. Still, this was yet another instance in which caring was not an advantage, just as Mycroft had been reminding this puzzling man for years. Caring, especially for someone as remarkable and unique as Sherlock, would only cause pain.

However... perhaps Sherlock was no longer entirely unique. And perhaps, considering Sherlock's reaction, his grief and panic, his caring had had a distinct advantage beyond Mycroft's wildest speculations.

Perhaps Sherlock's caring had done the impossible, and saved John Watson's life.

A second car, identical to the one that had brought Mycroft, pulled up. Hayes climbed out, a bag in his hands.

"Sir?"

"Has my brother been tended to?" Mycroft nodded in greeting and took the bag. He had had Hayes stop off to retrieve the contents, which he assumed - hoped, even - would be needed.

"He's been taken to the hospital, sir. My men had to sedate him, though, to get him into the car. I'm sorry."

Mycroft shook his head. "No matter. He is relatively unhurt, which is the only matter of importance. And the perpetrators?"

"In custody, sir." Hayes nodded.

"Excellent. Take them back to London."

"What about...?" he trailed off, stumbling over his words as he followed Mycroft across the pebbles.

"What about the fate of John Watson, you mean?"

"Sir, if he's another... if he's like Mr. Holmes..."

"We will discuss the matter once I know more," Mycroft said shortly. "You've done good work tonight; please arrange for our return to London."

"Yes, sir," he nodded and stepped away quickly, though Mycroft noticed him glancing over his shoulder, eyes scanning the length of the beach. He allowed a small smile to pull on his lips. Yes, it was a curious situation, indeed. He could hardly blame the man for wondering.

Mycroft strolled along the pebble beach, far from the bustling pier and its raucous crowds. He sensed rather than saw his flanking guards, though he knew innately that they were present, as they always were whenever he was (rarely) in the field.

There. Out in the water, which was reflecting the brilliant sunset on its rippling surface, was a man. Mycroft paused, leaning on his umbrella, and waited. The man seemed to have spotted him, for he was moving toward the shore now, movements uncertain. Mycroft made no move to assist him, knowing him to be more than capable, but instead tugged the towel from the bag.

"... Mycroft?"

He nodded in greeting. "John."

John Watson stumbled onto the dry pebbles, whole body shivering. Wordlessly, Mycroft held out the towel, which the shorter man seized and wrapped tightly around himself. His eyes were wide and lost.

"So..." he let out a half-hearted laugh and gestured down at his body, unclothed aside from the towel. "That happened."

Mycroft smirked. "Indeed. The question is, how?"

John shook his head disbelievingly. "I have no... I died, didn't I? ... Oh God, Sherlock. Did Sherlock see? Where is he? Is he alright?"

Mycroft held up a placating hand. "Sherlock is fine. He was... taken off-location before he could witness your passing."

"But he knows," John said, eyes narrowed and shrewd. "He knows I died. But... but did you tell him about... this?"

Mycroft grimaced. John was more perceptive than he sometimes gave him credit for. "I have not, yet. I thought that was a revelation best delivered by you."

John paced back and forth, bare feet unsteady on the pebbles. "I can't believe... It's just how Sherlock described it to me... You feel yourself dying, but then before you can be pulled all the way down, your life flashes before you, and then you're awake again in water. He said you end up in the nearest natural body of water, which of course right now is here..." he waved a hand toward the sea. "But... how? Why?" He looked up at Mycroft, beseeching. "What is going on?"

"John," he took pity on him, speaking softly. "I may have known Sherlock for longer than you, but rest assured I am far from an expert on these matters. I admit that when Sherlock gave you a blood transfusion, I considered the possibility that it could have unforeseen effects on you; however, the time-sensitive situation did not allow for caution of that sort. And Sherlock was desperate to save you. I doubt anyone could have convinced him not to help you. Furthermore, he assured me after the fact that a donation of his blood would _not_ change you, any more than a transfusion from any other donor."

John blinked. "But you do think the blood transfusion did this?"

"You tell me. I consider it the only logical explanation."

"Jesus," he breathed after a moment's reflection.

They stared at each other, for once on the same level, on equally uncertain ground. Simultaneously they smiled, a moment of helpless emotional release in the face of their impossible situation.

"Did you get those wankers who killed me, at least?" John asked then, adjusting the towel self-consciously.

Mycroft nodded, then handed him the bag. "Clothes for you. And yes, they are in our custody."

"Good," John frowned, eyes down as he clearly relived the last moments of his mortal life.

"Do not think on what has happened too hard just now, John," Mycroft murmured as they both headed for the car. "You've had a trying evening. I sense it will take time for you to come to terms with this."

"You can say that again," John laughed humorlessly. "I assume you're taking me to Sherlock." The way he said it could have been seen as a clarifying question, but the look in his eyes told Mycroft that had he said it to a weaker man, that man would have cowered and rushed John to Sherlock without a word. As it were, that was already the plan.

"Indeed. After that, perhaps the two of you can together resolve what has happened."

John nodded as he climbed into the backseat, the bag of clothes clutched tightly. Mycroft took the passenger side, and the driver pulled away. Mycroft risked a glance into the backseat moments before the privacy screen lifted to obscure his view. John was staring down at his hands as if he had never seen such a remarkable sight before, as if he could see through the skin to the veins pumping life-giving blood through him. However, there was one thought written all over his face. Sherlock.

* * *

Mycroft strode down the white, eerily-sterile hallways of Brighton's hospital, umbrella clicking on the floor. Freshly clothed, John followed half a step behind, trepidation thrumming through him like a ghostly physical sensation he couldn't quite locate on his person. Rather, it was everywhere, crawling about with anxiety. What if Sherlock was upset that this had happened, that John might be immortal? Or what if it wasn't a permanent condition? Or... what if John has just gone insane...? Well, that would actually solve everything, so never mind.

Riddled with these doubts, John hardly noticed Mycroft had stopped until he'd taken three extra steps down the hall. He paused, spun around, and smiled sheepishly at the taller man, who was cocking an eyebrow at him.

"I'll just check in with him, shall I?" Mycroft asked quietly. John nodded, suddenly feeling as if a tennis ball were lodged in his throat. Mycroft knocked softly, then entered the room. John leaned in to listen, though stayed out of sight. He and Mycroft had both agreed that springing this news on Sherlock may not work in their favor; better to let Mycroft speak with him first and assess how he was mentally.

"Sherlock?"

"Go away, Mycroft." Sherlock, if John was correct, sounded as if he had a bad head cold. Or something else. The thought of what the something else probably was made his heart clench.

"How are you?"

"I'll survive," Sherlock spat. "As you well know. Now leave me be. Don't you have criminals to deal with?"

"They are being transported back to London as we speak. How is your wrist? I thought from the CCTV footage that you had injured it in your altercation with that man."

"It's fine, just a minor sprain. Now leave me _alone_."

Mycroft sighed. "There will be a car waiting. You will be free to leave as soon as I verify a few things with your doctor. Now for all our sakes, please stay put. You have a visitor."

"Who?" Despite Sherlock's still-clogged voice, he sounded perplexed.

Mycroft ignored the question in favor of stepping back into the corridor. He shut the door to Sherlock's room and met John's gaze. "There are many things he is not saying, but he does appear to be mostly thinking straight. Though I am sure he is experiencing fallout he is refusing to let me see. Be gentle." John nodded; as if he needed to be warned about that. This was delicate. He turned his gaze to the door, a thin wooden barrier that was now the only thing separating himself from Sherlock, and from facing his new, astounding reality. Distantly, John heard Mycroft head off toward the nurses' station. Might as well get this over with. After a quick breath, John entered the room.

"Sherlock?" he murmured as gently as he could, hesitating in the doorway.

The man's head whipped up at such a high velocity John was surprised he did not injure himself. His eyes - which were suspiciously red and swollen, confirming John's fears - flew wide open as he gaped. "J-John?" his voice came out strangled and shocked.

"It's me," he said, as calmly as he could. "It's alright, Sherlock."

"But..." Sherlock stammered, watching as John strode a few more steps into the room to stand before Sherlock, who had snapped upright from his perch on the edge of the hospital bed. "I don't understand, this... this can't be real," he finished after several beats of silence, his voice suddenly surging back to its full power. "I saw you die!"

"Now you know how it felt for me." How the tables had turned since then. "You didn't stick around for the impossible finale, did you? Lucky for me, your so-called brother cleaned it all up."

Sherlock still looked dumbfounded, an expression John felt rather privileged to see. It was rare he ever showed such an emotion on his face. He seemed to analyze John for several long moments, then spun about on his heel and began pacing frantically, chest heaving. Neither one of them spoke for long minutes, John sensing his friend was deep in his mind palace, parsing the new information about John with what Sherlock knew about himself, calculating and analyzing. Perhaps not believing.

"Sherlock," John tried again as he watched his flatmate's frenzied movements. "You didn't see wrongly, if that's what you're thinking. You know what happened."

"Then what are you? A hallucination brought on by shock and grief?" The reply was harsh, snappish, and instantaneous. "Some malicious poltergeist sent to torment me?"

John flinched at that. "No," he murmured. "I'm sorry I hurt you. I didn't mean for this to happen, I didn't even know it would. But I'm here now, it's alright-"

"John," Sherlock cut him off, eyes flicking up to meet his, full of years more pain than John could fathom as his pacing ground to a halt. "Of course you didn't mean to die. Few people do. And you, you are good and kind and would never intentionally cause me pain. But what you fail to understand is that for me, pain and loss is unavoidable. Every connection I have ever made, every friend and acquaintance, I have been forced to either part ways with them too soon or watch them die. None of them meant to die either, but sickness or time or their own problems caught up with them. None of the ones I willingly left understood why I had to disappear. And those I shared this secret with... Well, you are among the elite, John. I have had many acquaintances in my life, but fewer than a handful who knew the truth about me. But they are gone, as I knew they would be someday. You have no idea what that is like," he whispered, head hanging. He seemed incapable of meeting John's gaze. "By now, I am hardwired to view everything from the standpoint of an immortal, never letting myself get too close. But you..." his hands gestured at John's general person, and his eyes flickered up. "I found myself closer to you than I have ever been to anyone, without realizing or intending to. I cannot even pinpoint just what it is about you that makes you different. And losing you... I have never felt more cursed in my life, shall we say, and leave it at that."

"Sherlock..." John stepped closer, bringing his hands up to grip Sherlock's forearms, to ground this impossible man with tangible physical contact. Just as Sherlock had, months ago, on a doorstep somewhere in central London after having bled out in John's arms. Again, John had to marvel at how far they had come, at how much had changed.

"John," he breathed, and John thought he might be shaking. "Tell me what is going on, because despite my unparalleled deductive powers-" John nearly rolled his eyes at that. "-I cannot understand what could have happened that you're here, seemingly unharmed."

"You gave me your blood, didn't you?" John asked by way of answering, hands still clutching the taller man, hopefully in a soothing manner.

Sherlock hesitated, a familiar crease forming between his brows. "Yes, but..."

"But I died anyway," John continued, barreling on because saying it was helping him comprehend it too, helping the reverberating shock ease in intensity a bit. "I died, and then I came back. In the ruddy sea, which by the way was freezing. Still, at least it wasn't the Thames. I've heard enough about it from you to hope I never end up in there."

Sherlock was gawking again, his dazzling green-gray eyes, still tinged with red, going wide with disbelief. "No..."

"Sherlock, Mycroft thinks it isn't entirely inconceivable," John explained. "But you know more about it than he does... what do you think? Was that a one-time thing, or... am I like you now?"

"I..." Sherlock bit his lip. A moment passed between them then, as they clutched at each other, trying to decipher the riddle that was their lives. John stared at Sherlock, desperate to hear the detective's explanation. There had to be one, and if anyone would have it, it would be Sherlock. "I..." Sherlock repeated. "This has never happened before."

"What do you mean?"

Sherlock pulled back and resumed pacing, stepping a few feet away and then swishing back, then repeat. Contrary to last time, though, this pacing was more purposeful, movements energized rather than devastated. When he began speaking, his hands gesticulated as if of their own accord, as they always did when Sherlock's mind was racing.

"I've been in situations before when someone needed my blood, and this never happened. In one case the person... didn't make it, and the other survived that incident but still died several years later of perfectly boring old age." He shook his head as if trying to shake cobwebs from his brain. "This shouldn't be possible." He looked up again, gaze boring into John. "Why you? Are you truly immortal now? Is it temporary? Would you need more of my blood to supplement this condition? Or..." he seemed to choke suddenly, swallowing hard. "Have you always been like this?"

John started. He hadn't considered that. But after a moment's consideration, he shook his head. "No. When I was shot in Afghanistan, I was dead for almost two minutes. No pulse, no physical responses to any stimuli. They were going to move my body off the operating table when my heart started beating again. Not an entirely unheard of thing, but still nothing like your... condition. So there's no way I've been like you since the beginning. When I saw you die, you disappeared in seconds of your pulse stopping, and according to Mycroft, what happened to me today was the same."

Sherlock blinked about six times in rapid succession. John waited, full of more trepidation, confusion, and fear than he thought he had ever felt in his life, while his flatmate appeared to dive back into his mind palace. He did not come up for air, so to speak, until John gave in and rubbed Sherlock's arms with his thumbs. "Hey," he sighed, jolting him back to the present. "I'm sorry I died, you know."

Sherlock huffed a soft laugh, but John could see in his eyes he wasn't entirely amused, the shocked grief still present on the fringes. "It isn't anything I haven't already done to you," he quipped half-heartedly.

That made John smile, his first real one since before his death and all that had come after. Sherlock hesitated, but then smiled back.

After a minute or so of coaxing, John convinced Sherlock to sit perched on the edge of the bed, John beside him. Now that some of the initial shock had worn off for both men, and they had progressed to something closer to the discussion stage, Sherlock appeared to be compulsively touching John. When he wasn't using his hands to send frantic texts Mycroft or to fiddle with the bandage and ice pack wrapped around his wrist, he pushed his knee against John's. When a hand was unencumbered, however, his fingers pressed against John's wrist over his pulse point. John allowed it, remembering how he had felt the very same way on the night after Sherlock's revelation. Finally, he simply slipped his fingers between Sherlock's and squeezed.

"Why you?" Sherlock breathed again after a long silence, eyes fixed on their hands. "Why did my blood make _you_ this way, when it didn't with anyone else? Will it even last?"

John shrugged, and as Sherlock looked over at him, a surge of acceptance, peace, and affection came over John. "I don't know," he whispered, shifting closer to his detective. "Sounds like a promising experiment, though, don't you agree?"

Sherlock laughed softly. "Indeed."

"And if my hypothesis," John paused to raise his eyebrows dramatically, eliciting another chuckle. "-proves to be correct, you and I will have lots of time to figure it out."

The smile Sherlock gave him then was far less pained, far more hopeful than any expression John had ever seen him make. The deep and pervading sadness was still present in his eyes, yes, but some of the loneliness seemed to have retreated. Sherlock settled in closer to his side then, and John smiled. If this was to be his life, chasing after an insane immortal who possessed an uncanny passion for mystery, then so be it. He felt that he could handle it. Besides, he'd have plenty of time to hone this skill.

"John," Sherlock breathed, hand finding John's wrist again. "I'm glad it's you."

John just smiled and laid his other hand over Sherlock's. "At least it's not Mycroft, right?"

Their laughter rang throughout the room, and John knew that whatever happened in the future, in the decades and centuries and even perhaps millennia to come, as long as they had this, their bond, they would be alright.

* * *

 _One week later..._

"Oi, I told you not to fiddle with that stuff," John called from the kitchen. Sherlock snapped up, scowling.

"You really want to put this much in? You'll fill dozens of books in a century at this rate."

John rolled his eyes, striding across the room to deliver Sherlock his cup of tea, then settled down on the sofa with his own. "I want to document my life when I was normal. If I live to be as old as you, I'll want to see this stuff."

"Mortal," Sherlock corrected, flopping down next to him, somehow managing to keep all the tea in his cup despite his careless motions. "Your life when you were mortal, John, because I can assure you have never been remotely normal."

"Oh, sod off, git," John grinned at him. He turned his gaze to the table in front of them, where artifacts of his own were spread, ready to be placed in an album much like Sherlock's. Family photos, his birth certificate, first driving license, diplomas and medals, army photos, and a few trinkets. Then there were several pictures of life with Sherlock, clippings of newspaper articles about cases solved, and a few printouts of the blog. He hadn't started assembling any of it yet, still compiling and curating the items, sifting through his life and trying to decide which bits he should document or lose to time. It was daunting; he didn't have a clue how Sherlock could have made his album so sparse.

Both of them were still operating under their precarious assumption that John was indeed immortal. There could be no proof short of a literal suicide mission, which neither man was keen to try. Especially since they were now back in London, and John was flat out refusing to even hear the word "Thames" mentioned. He knew the depths of the river were possibly in his future, but that hardly meant he wanted to _think_ about it. So since there was no proof to be had short of drastic measures, the two men were simply waiting. Only the passage of time would tell, which irritated Sherlock to no end, the impatient nutter.

John glanced over to see Sherlock reading a clipping John had chosen. He knew Sherlock was trying not to get his hopes up, but he occasionally caught the other man staring at him intently, as if trying to _feel_ if John was aging. And while the thought was terrifying, overwhelming, and practically inconceivable, John found himself desperately not wanting to let Sherlock down. He would never forgive himself if he were the reason that hopeful sparkle in Sherlock's eyes ever died.

Footsteps on the stairs prevented John from saying something reassuring (and probably embarrassing), and they both looked up to see Greg Lestrade, looking harried.

"Hey," he greeted. "I, um... well, I've got a case for you."

"Have you?" Sherlock stood, sounding eager. Though he still had his wrist in a brace, John could tell his mind was already rebelling at the week without cases.

"Yeah," Lestrade looked puzzled. "The thing is... it has the same MO as a locked room murder-suicide cold case." He swallowed. "From 1892. Down to details only the police could have known, as far as we can tell."

John whipped his head around to stare at Sherlock, and sure enough, the man was practically vibrating out of his skin in excitement. "Lestrade," he breathed, a grin tugging at his lips. "You've outdone yourself."

The DI chuckled. "Right, okay. I figure you'll follow in a cab?"

Sherlock seemed momentarily immobile from delight, so John nodded. "Yeah, text the address." He moved to grab their coats and tossed Sherlock's toward his chest as Lestrade left again. "Oi, wake up Sherlock."

"John," Sherlock was grinning when John looked up. "A locked room copy of a cold case. This is fantastic, it's amazing... it's... it's Christmas!"

John laughed fondly at his nearly childlike reaction. "Let me guess. You want to solve both?"

"There's always a trail, John," Sherlock replied, eyes sparkling as he tugged on his coat. "And after all, we have all the time in the world."

John smiled. Oh, how he hoped so. "So. When do we start?"

Sherlock grinned. "Now, obviously."

They chased each other out of the flat then, laughter mingling with their footfalls, both feeling free on the threshold of the rest of their lives.

They had a long story to tell together, after all.

The End.

* * *

 **I try to give credit where due, and since so much of the plot is inspired by this post: henrymorgandaily . tumblr . com . post/111119431112/wingsofnight-henry-saves-jos-life-with-a-blood, I felt it necessary to make note of it. Thanks to the OP of that; you're a lovely person, and I hope you don't mind that I riffed off your idea a bit.**

 **Please review!**


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